a. Field of the Invention
This invention relates to applying strapping band around an object such as a package, so overlapping portions may be subsequently fusion-bonded while the band is held tensioned around the object.
B. Description of the Prior Art
Conventional band guiding devices of the arched type have an arcuate or loop-shaped guide channel following the contour of the arch around the article being banded. The channel has a radially inwardly open side with resilient or flexible strips of rubber, plastics, or spring steel along opposite edges, through which the band is withdrawn when it is reversed and tensioned about the article. Examples are shown in U.S. Hall et al U.S. Pat. No. 2,853,938, U.S. Mosey et al U.S. Pat. No. 2,968,234, and U.S. Kurihara U.S. Pat. No. 3,752,237.
Other previously known band guiding devices have a guide channel or guide frame closed by an elastic or hinged opening-and-closing plate so as to guide the band in the form of a loop about the article. Examples are shown in Japanese Utility Model Publication No. 2400/1971, Japanese Unexamined Utility Model Publication No. 122389/1973, and Japanese Patent Publication No. 10837/1973. These prior devices, however, are prone to malfunction if the band width differs from that for which the guide was designed, causing the band to stick or catch, or slip out of the guide during the forward feeding operation. Further, these prior band guiding devices sometimes cause the band to be drawn out of the arch discontinuously and wrap in an insulating or meandering path around the article when the band is reversed and tightened, making it difficult or impossible to complete every strapping operation with the required amount of tension in the band. These problems become particularly severe at high band feeds, often causing the machine to operate at considerably less than full capacity.
To overcome the above problems, an improved hinge construction has been developed for high speed strapping machines, this being shown in Japanese Utility Model Publication No. 23840/1969 and Australian Pat. No. 433,980. However, this construction requires high manufacturing precision and is costly. Another hinge construction is disclosed in Japanese Unexamined Utility Model Publication No. 28487/1972 but banding operations carried out with it may be inconsistent because the band may be drawn out of the arch erratically or all at once when it is reversed and tensioned. An attempt to correct that has been described in Japanese Unexamined Patent Publication No. 92197/1973 which discloses means for applying continuous hold-back resistance to the band when it is drawn out, to cause the band to be drawn out smoothly and steadily and not all at once. There is still, however, the problem of increased manufacturing costs even though this particular construction is an improvement over the others mentioned.
Summarizing, prior strapping band guides have often caused the band to be guided erratically so it can encounter considerable resistance or slip out of the guide during the forward feeding operation. Further, they have not been reliable in releasing the band smoothly and progressively around the arch when the band is reversed and tensioned. Prior to the present invention, attempts to correct these shortcomings have resulted in constructions requiring high precision manufacturing operations, complex mechanisms, and objectionably high costs.